Ok we will go the observation method.
I observe that the stars rotate in the sky in relation to the earth and not each other.
throughout history we have identified constellations in the night sky and can chart them in relation to each other for the entire night sky
in the northern hemisphere the stars will rotate in one direction in the southern the other. and near the equator they pass from east to west.
Now for why.
Quote from: ThePenguin on Today at 08:33:39 AM
So if the stars are a fixed sphere that rotates around the earth (or the earth rotates inside the sphere either way works) then the only explanation of the sky rotating in different directions is the earth is round.
The universe is three dimensional. Obviously. Why does it follow that the earth has to be round? That's just a total nonsense.
any spinning object will appear to spin in different directions based on what side you look at.
take a bicycle wheel, it's rolling down a hill. on one side it's going counter clockwise and on the other it's going clockwise same with a ball.
If I'm on one side of the wheel I will only see fixed objects turning in one direction.
now if I'm on a sphere the fixed objects will rotate in one direction then I travel to the other side, the fixed objects will rotate in the opposite direction .